The major objective is to improve understanding of the endocrine and para-endocrine activities of the lungs by defining structure-function correlations of the cells that make up the alveolar-capillary unit and its interstitium. Particular focus will be placed on endothelial cells of the microcirculation and associated pericytes and interstitial cells. The endothelial cells will be examined firstly in terms of subcellular sites of angiotensin coverting enzyme (kininase II). In addition, endothelial cells, pericytes and other interstitial cells will be examined for their abilities to synthesize prostaglandins and/or related substances such as thromboxanes A2 and B2. The studies will coordinate techniques of advanced electron microscopy with biochemistry, freeze-etching, autoradiography, cytochemistry, immunocytochemistry and cell culture. By proceeding in this way, it should be possible to help define the physiologic significance of the endocrine and para-endocrine activities of the lungs and to understand the pathologic consequences that may arise through dysfunction of these activities.